Control Flow

For Loops

A for loop repeats with a counter when the number of steps is known.

loop counter A loop counter changes each time the loop repeats.

For Loops

limit
ForLoop.cs
Replay: real traced execution (multi-file project)
using System;

class Program
{
    static void Main()
    {
        int limit = 4;
        int sum = 0;

        for (int number = 1; number <= limit; number++)
        {
            sum += number;
        }

        Console.WriteLine($"limit={limit}");
        Console.WriteLine($"sum={sum}");
    }
}

using System;

class Program
{
    static void Main()
    {
        int limit = 2;
        int sum = 0;

        for (int number = 1; number <= limit; number++)
        {
            sum += number;
        }

        Console.WriteLine($"limit={limit}");
        Console.WriteLine($"sum={sum}");
    }
}

using System;

class Program
{
    static void Main()
    {
        int limit = 5;
        int sum = 0;

        for (int number = 1; number <= limit; number++)
        {
            sum += number;
        }

        Console.WriteLine($"limit={limit}");
        Console.WriteLine($"sum={sum}");
    }
}

  1. limit ← 4, sum ← 0

    4{5    static void Main()6    {7        int limit→ 4 = 4; //@limit=2, 58        int sum→ 0 = 0;

  2. sum ← 1

    pass 1 of 4
    10for (int number1 = 1; number <= limit4; number++)11{12    sum→ 1 += number1;13}
    All 4 passes — pass 1 is the card above
    passnumbersum
    111
    223
    336
    4410

  3. Console.WriteLine($"limit={limit}");

    15    Console.WriteLine($"limit={limit4}");16    Console.WriteLine($"sum={sum10}");17}
    outputlimit=4
sum=10

  1. limit ← 2, sum ← 0

    4{5    static void Main()6    {7        int limit→ 2 = 2;8        int sum→ 0 = 0;

  2. sum ← 1

    pass 1 of 2
    10for (int number1 = 1; number <= limit2; number++)11{12    sum→ 1 += number1;13}

  3. sum ← 3

    pass 2 of 2
    10for (int number2 = 1; number <= limit2; number++)11{12    sum→ 3 += number2;13}

  4. Console.WriteLine($"limit={limit}");

    15    Console.WriteLine($"limit={limit2}");16    Console.WriteLine($"sum={sum3}");17}
    outputlimit=2
sum=3

  1. limit ← 5, sum ← 0

    4{5    static void Main()6    {7        int limit→ 5 = 5;8        int sum→ 0 = 0;

  2. sum ← 1

    pass 1 of 5
    10for (int number1 = 1; number <= limit5; number++)11{12    sum→ 1 += number1;13}
    All 5 passes — pass 1 is the card above
    passnumbersum
    111
    223
    336
    4410
    5515

  3. Console.WriteLine($"limit={limit}");

    15    Console.WriteLine($"limit={limit5}");16    Console.WriteLine($"sum={sum15}");17}
    outputlimit=5
sum=15

Add One Through the Limit

  1. limit starts at 4.
  2. sum starts at 0.
  3. The loop runs with number from 1 through 4.
  4. Each pass adds number to sum. | Number | Running sum | | --- | --- | | 1 | 1 | | 2 | 3 | | 3 | 6 | | 4 | 10 |

Exercise: ForLoop.cs

Use a for loop to add numbers from 1 through a limit and print the sum